(a) Technical Field
The present invention relates to an apparatus for preventing overcharge of a battery in which power to the battery is blocked when the battery is over-charged.
(b) Background Art
In general, electric vehicles, hybrid vehicles or fuel cell vehicles use high-voltage batteries to supply electrical energy for powering these types vehicles. High-voltage batteries consist of a battery pack to produce high-voltage by connecting a plurality of unit cells or modules and therethrough generates high power using the high-voltage battery.
Battery packs are often stacked to provide higher density so they can be used in rectangular type or pouch type cells and the like having low individual capacity. Unit cells (battery cells) of the battery pack are often lithium ion cells that provide high power at a low capacity.
However, the lithium ion cells are often unsafe in vehicular implementations. That is, in particular in the pouch type cells, the mechanical strength of the cell case is low and when a sealing part/gasket is separated, leakage of flammable material such as electrolyte may be emitted and thus increases the risk of fire.
In particular, since the electrolyte is injected into the inside of the cell, when the battery is over-charged, the voltage rises and the electrolyte inside is more rapidly decomposed due to overheating which generates flammable gases as a result. Accordingly, the risk of fire and explosion of the battery are increased due to a swelling phenomenon of the pouch itself.
In this regard, when the swelling phenomenon occurs due to overcharging of the battery, a technology for blocking power of the battery by force has been proposed. FIG. 1 illustrates prior art for blocking battery power in which expansion stress is concentrated in a connection part of the battery cell 1 or electrode terminal 2 of a unit module, when expanding due to the swelling of the battery cell 1 occurs. In this case, a portion of the connection part is configured to include a weak structure in terms of volume expansion so that when swelling is equal to or greater than a predetermined value, a short circuit may occur when the portion of the connection part of the electrode terminal 2 bursts.
However, since the connection part of the electrode terminal is configured to include a weak structure, the connection part of the electrode terminal can burst due to unexpected physical force or vibration and the like as well as expansion operation of the battery cell due to weakening of durability.